This invention relates to generator systems and, more particularly, to an arrangement having an arc fault device that electrically isolates a selected portion of the generator system in response to a detected electrical event.
Vehicles, such as an aircraft powered by a gas turbine engine typically include a generator mechanically coupled to the engine. A generator controller controls operation of the main generator by providing electrical power to modulate the generator output. A second generator is mechanically coupled to the main generator and produces electrical power when the main generator operates. The second generator, typically a Permanent Magnet Generator (PMG), delivers the electrical power to the generator controller as a source of electrical power to control the main generator. The second generator provides continuous electrical power while the gas turbine engine operates, and is often referred to as an “uninterruptible” electrical power source to the generator controller.
In conventional generator systems, the generator controller often includes electrical hardware to selectively control the main generator. The electrical hardware may experience electrical faults that increase impedance through the generator controller. In the event of an electrical fault, the uninterruptible power source will continue to deliver electrical power. Disadvantageously, this may result in an undesirable increase in the temperature within the generator controller, which may cause smoke. Smoke in this case is a significant issue on an aircraft as it cannot be cleared using normal smoke clearing procedures. Normal smoke clearing procedures involve selectively turning of electrical power busses and observe if the some is abated. Since this fault is being sourced from an uninterruptible power source it cannot be cleared in this manner and it is beneficial that the generator controller provide the fault clearing function.
Conventional generator systems utilize a fuse or a circuit breaker in the generator controller that respectively blows or trips to electrically isolate the uninterruptible power source from the generator controller to avoid a temperature increase beyond a predetermined level. These systems may be somewhat unsuccessful as faults are typically of relatively high impedance, which may not draw sufficient electrical power to reliably blow the fuse or trip the circuit breaker. Conversely, a highly sensitive fuse or circuit breaker may be prone to undesirably blowing or tripping during what should be considered a normal operational condition.
Accordingly, there is a need for a generator system having an electrical arc fault device that determines an electrical fault and reliably isolates the uninterruptible power source from the generator controller if an electrical fault is detected.